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Open Access Publications from the University of California


The concept of the Vertebrate Pest Conference originated in early 1960 from discussions among representatives of the University of California; the California Dept. of Fish & Game; the California Dept. of Agriculture; the California Dept. of Public Health; and the Branch of Predator and Rodent Control, Bureau of Sport Fisheries and Wildlife, U.S. Fish & Wildlife Service. The original participants recognized that few published documents on vertebrate pest control were available, as such information was typically contained within in-house reports of the various agencies that were largely unavailable and unable to be cited. Dr. Walter E. "Howdy" Howard of UC realized that having a conference would permit a Proceedings to be published, in which this information could be made widely available.

To plan such a conference, the organizing group, chaired by Dr. Howard, became the Vertebrate Pest Control Technical Committee, which arranged and hosted the first "Vertebrate Pest Control Conference" held in Sacramento on February 6 & 7, 1962. The planning committee formally became an incorporated non-profit entity in 1975, and the Vertebrate Pest Conference is now held in late winter or early spring every two years. It is the most widely-recognized conference of its kind worldwide.

Detailed histories of the development of this Conference are found in these publications:

Salmon, Terrell P. 2012. VPC: Fifty Years of Progress? Proc. Vertebr. Pest Conf. 25:3-6.

Marsh, Rex E. 2008. A History of the Vertebrate Pest Conference. Proc. Vertebr. Pest Conf. 23:310-326.

Gorenzel, W. Paul. 2004. Opening Remarks - A Retrospective Look at the Vertebrate Pest Conference. Proc. Vertebr. Pest Conf. 21:1-2.

Howard, Walter E. 1982. Twentieth Anniversary of Vertebrate Pest Conferences in California. Proc. Vertebr. Pest Conf. 10:235-236.

Howard, Walter E. 1962. Opening Remarks – Vertebrate Pest Control. Proc. Vertebr. Pest Conf. 1:1-7.


Vertebrate pest management and changing times

The author describes recent trends in development, use, and regulation of vertebrate pesticides, given the current attitudes and philosophies of American society’s opinions regarding environmental awareness, pollution, endangered species protection, and pesticide hazards. He notes the relative absence of development of new vertebrate pest control technologies during the last three decades, in part because of the high cost of pesticide registration, a function of increased regulatory oversight of pesticides. He also takes issue with over-zealous environmentalism that is not based on scientific fact. The restrictions placed by the Federal government on tools and materials used for predator control during the 1970s are discussed, as well recent actions that have eased some regulations, thus leading to registration of several new rodenticides as well as new efforts in developing materials for predator control.

Alpha-chlorohydrin (Epibloc): A toxicant-sterilant as an alternative in rodent control

Alpha-chlorohydrin (EPIBLOC) introduces a new form of rodenticide - the toxicant-sterilant. EPIBLOC, as a pest control product registered and used in some countries, changes the concept of chemosterilants from theoretical to practical. The active ingredient also acts as an acute toxicant in the control of rodents. It is effective on both sexes and all age groups. Alpha-chlorohydrin is rapidly absorbed and metabolized; therefore, it is neither a secondary toxicant nor a cumulative toxicant. Another unique biological characteristic of this compound is its species specificity with regards to male sterility. First, only sexually mature males are rendered sterile through the development of lesions in the epididymis, and second, male sterility is restricted to rodent species. Adult males of some mammalian species become temporarily infertile when treated with nonlethal doses of alphachlorohydrin. These males regain their fertility shortly after the end of treatment. Males from seven rodent species are known to develop permanent sterility. Of all the species tested Rattus norvegicus has been subjected to the most research. The single oral dose which produces temporary infertility in this species is 15-20 mg/kg of body weight; the dose that produces permanent sterility is 90-100 mg; and the LD50 is 150-160 mg. Field tests with EPIBLOC on a variety of rodent pests have provided a body of practical information. Namely: (i) effective as a toxicant-sterilant with a single administration of bait; (ii) reduction in the rodent population due to death ranges from 70-95%; (iii) the reproductive rebound phenomenon commonly observed after baiting with toxicants is prevented due to the sterilant property; (iv) 80-95% of surviving adult males are sterile and act as a deterrent to repopulation; and (v) the species specificity for sterility, the metabolic activity and the biodegradable characteristics allow it to be used under many environmental conditions.

Bromethalin--a promising new rodenticide

Bromethalin is a unique, highly potent rodenticide exhibiting a mode of action different from anticoagulant rodenticides. Bromethalin provides a lethal dose to rodents in a single feeding with death generally delayed two to three days. Rodents do not discriminate against bromethalin bait; therefore, excellent bait acceptance is achieved with no prebaiting. Field studies have shown bromethalin bait to be highly efficacious against Norway rats and house mice under a variety of field conditions. Laboratory and field trial data indicate bromethalin is effective against known anticoagulant-resistant rodent populations. Toxicological data indicate bromethalin bait is relatively safe to nontarget species as well as to the environment.

Bird limes and rat glues--sticky situations

In antiquity, sticky materials were widely used for catching small birds for food and sport, but this practice is now illegal in most industrial nations. The most widespread use of sticky materials is in "glueboards" to catch rats and particularly mice. Their popularity has increased with the negative public attitude towards use of pesticide chemicals. Early materials were made from latex and gums of many trees, but current ones also use industrial chemicals like polyethylenes and polybutenes. They have most of the advantages of traps but have some disadvantages. Their use may be limited by temperature, moisture, dust, vapors, etc. The proper methods of handling, placement, and cleanup of rodent glueboards are discussed.

The urban coyote problem in Los Angeles County

Extensive, urban development of hillside areas in Los Angeles County has created an undesirable human interface with coyotes (Canis latrans). Plentiful, readily available household garbage, pet foods, and water have spawned abnormal numbers of bold coyotes that have adopted residential properties and the human environment as ideal habitat. Consequently, at least six persons have been attacked, including the death of a three-year old child, during the past three years. Selective use of padded steel traps, shooting, and public education are presently being used in problem areas by the Agricultural Commissioner in an attempt to reindoctrinate these predators into returning to their natural habits.

The use of fences for predator damage control

The development of exclusion fencing has been extensive in Australia in attempts to reduce losses of crops and livestock to rabbits (Oryctolagus cuniculus), dingos (Canis familiaris var. dingo) and other species. Restrictions on other damage control methods have led to increased efforts in the United States to utilize such fences for protection of crops and livestock from dogs (Canis familiaris), coyotes (Canis latrans) and other species. Electric fences have occasionally been used to protect apiaries from black bears (Ursus americanus) and to protect some wildlife species from carnivores. Varied fence types include conventional netwire or combinations of net and barbed wire, high-voltage electric wires, and conventional fences modified by addition of electric wires. Fences appear to be most useful and cost-effective on small open pastures with intensive production and appear to be least successful on large pastures with low production and high vegetative cover, which restricts removal of predators. Fences may be helpful in directing predator travel to areas where other control methods can be applied. Limitations on the use of exclusion fences include construction costs and the inability to exclude some predators or to remove them from fenced areas. Regulations related to protection of wild species such as pronghorn antelope (Antilocapra americana) may prohibit construction of effective exclusion fences, particularly on public lands. Difficulties and costs of fence maintenance are related to terrain, soil types, dense vegetation, fence damage by livestock and other animals, heavy snows, floodwaters and other causes. Predators gain access through damaged fences, malfunctioning electric fences, or by jumping over or digging under. Data indicate that where predators tend to be contained within such enclosures, fences may serve to increase losses to predation rather than to reduce them.

Monofluoroacetic acid (Compound 1080), its pharmacology and toxicology

The molecular mechanism of toxic action of fluoroacetate is analyzed in the perspective of scientific developments of the past 30 years. Stereospecific enzymatic conversion of fluoroacetate via fluoroacetyl-CoA + oxalacetate to (-)-erythrofluorocitrate in mitochondria is the metabolic pathway that converts the nontoxic fluoroacetate to the toxic intracellular effector molecule. The mode of toxic effect of (-)-erythrofluorocitrate cannot be equated with its reversible inhibitory effect on a mitochondrial enzyme (aconitase) as had been originally thought by Peters (1963) and is still propagated in textbooks. Instead, the chemical modification of inner mitochondrial membrane proteins by (-)-erythrofluorocitrate, comprising a novel, as yet incompletely understood biochemical mechanism, is the molecular basis of toxicity. Research in this new area may eventually explain selective (species--dependent) toxicity, the development of resistance to this poison and can lead to the scientific basis of the development of antidotes.

The role of USDA in animal damage control

The impact of vertebrate animal damage on agricultural production of row crops, forests, horticulture, poultry and livestock production, other wildlife, health of humans and domestic animals, and the protection of human interests is a vital concern of the U.S. Department of Agriculture. The Department recognizes that it is an old and complex problem that does not lend itself to easy answers. Animal damage problems will continue to be a significant concern of USDA and will probably always be controversial, requiring intensive research, educational, regulatory, and assistance programs. The objectives of the Department are to develop and maintain viable programs in animal damage control that are safe, effective and environmentally sound and to cooperate with programs of other departments and agencies, both federal and state, to alleviate the impacts of animal damage on people and their interests.

A tiger problem in India

During the past decade, India has done wonders in re-establishing populations of rare and threatened wildlife. Project Tiger, initiated in 1973, has stimulated a successful conservation movement in India. But tigers, like all animals, do not recognize man's property lines and, as populations increase in the forest reserves, more and more tigers forage outside of the parks, killing livestock and people. The current methods and regulations of dealing with troublesome tigers (and elephants) that stray from the sanctuaries due to overpopulation social pressures, lack of food, old age, or other reasons may soon become inadequate as the value of human life increases and for other reasons. Whenever wildlife fs being protected, the population must also be managed and controlled as needed.

Snares for predator control

The use of snares predates recorded history. The snare was first used when ancient man realized that an association between a tightening loop of vine and an ensnared animal was something which he could construct and repeat. The current increased interest in snares has been a result of restricted chemical tools in animal damage control resulting in a new look at old mechanical methods. The increased value of pelts of predators has brought efforts by private trappers to improve snaring as a tool. As a result, the ancient art of snaring has been greatly improved over the last decade. New snare locking mechanisms, improved snare cables, swivel and holding systems, and placement strategies have resulted in snaring becoming a very useful and reliable method for animal damage control and fur harvest. It has become an efficient alternative for leghold traps and M-44s in many situations where weather makes these tools inoperable. The versatility of snares has long been overlooked. They are weather-resistant, can be selectively set and located and constructed with break-away devices to protect against holding livestock and nontarget animals. Snares can be set in killing or live-trapping arrangements. The cost of snares is low, and maintenance is equivalent to or less than for steel traps. Snares deserve another look as a tool in controlling livestock damage due to coyotes, fox, bobcat, mountain lion, and bear. They can be used on most other problem mammal species as well.

Guard dogs and gas exploders as coyote depredation control tools in North Dakota

Guard dogs and as exploders have been successfully used in North Dakota to protect sheep from coyote (Canis latrans) depredation since the mid-1970s. They have been used in addition to other lethal and nonlethal control tools. The U.S. Fish and Wildlife Service gathered information from field testing and landowner interviews to measure their effectiveness. Guard dogs reduced the rate of depredation by 93 percent on the 36 ranches surveyed. Gas exploders deterred coyotes from depredating on 30 ranches an average of 31 days during the 1980 and 1981 grazing seasons. An increasing number of sheep producers are using these control methods to reduce losses and become less dependent on a publicly funded damage control program.

Mountain lion predation on domestic livestock in Nevada

The mountain lion has long been considered a serious predator on domestic livestock, primarily sheep, in the state of Nevada. For the past five years (FY77-81), documented losses to lions have averaged 375 animals. While this number is not large, most losses are sustained by only a few individual livestock operators, and the losses constitute a serious economic hardship for these individuals. An average of 23 lions have been taken in response to livestock depredation complaints during each of these five years. Controlling livestock loss to mountain lions is the responsibility of the Animal Damage Control branch of the U.S. Fish and Wildlife Service. ADC personnel work in cooperation with the Nevada Department of Wildlife, Nevada Predatory Animal & Rodent Control Committee and livestock producers in an effort to keep both livestock losses and the number of lions taken on depredation complaints at an acceptable level.

Predator problems when using sheep and goats in managing brush on rangelands

Rangelands occupy a large portion of the western United States and the world. Grazing by ruminant animals provides the only means of obtaining usable products from these lands. Sheep and goats are more efficient producers, better adapted to many ranges, and are useful in controlling or manipulating shrubs and other undesirable vegetation which results in improved range conditions and increased water yields. There has been a general decline in sheep and goat numbers and a shift toward cattle. Predation has been a major factor in the abandonment of many sheep and goat operations and the shift to other livestock. A viable range sheep and goat industry can survive only with an adequate predator management program that includes all methods of protecting livestock as well as all available lethal methods.

Development and evaluation of methods to reduce rat damage to coconut in the Philippines

Based on findings from studies conducted in the Philippines over a span of almost a decade, primarily by scientists at the Philippine National Crop Protection Center, crown-baiting (wherein bait containing anticoagulant is placed monthly in the crowns of some palms in a coconut plantation), holds the potential of providing highly economical protection from rat damage. The success of the method in various field trials appeared related, in part, to selective removal of rodents that feed in the palms and to the use of baits that were preferred over growing nuts. Studies have also indicated that only 10% or less of the trees may have to be baited for effective control, although additional field trials are needed to confirm the optimal levels of treatment for different coconut-growing regions in the Philippines. Based on findings from the studies, fallen, rat-damaged nuts may represent only a small portion of the damage that rats inflict on coconut palms in the Philippines.

Traditional approaches for protecting cereal crops from birds in Africa

Despite the recent emphasis in Africa by national and regional plant protection organizations to control pest birds, traditional farmers usually are still left to their own initiative, as they have been for centuries, to protect their crops. These farmers employ many ingenious visual and oratory frightening techniques, barriers, agronomic planting or harvesting modifications, and bird population-suppression methods. Under some circumstances these methods can reduce damage. However, their effectiveness is subject to such variables as the season of the year, the type and maturation stage of the crop, the pest species and its abundance, the size and ownership of the field, and the diligence and enthusiasm of the bird scarers. The inability of farmers to consistently and successfully protect their crops from birds encourages feelings of frustration, and often leads to their abandoning farming. Clearly practical, economical, and applicable solutions are needed by traditional farmers if future food production goals are going to be met. Research and extension can provide these solutions.

Solving tree squirrel debarking problems in Taiwan--a review

Extensive forest conversion of the low-valued natural hardwood forest into coniferous plantations is the possible cause of the critical problem of squirrel debarking. The tree squirrel that causes the major damage is the red-bellied tree squirrel (Callosciurus erythraeus). Conifers are more susceptible to the damage than are hardwood species, especially the exotics. Intermediate-aged plantations appear to have the highest debarking. More damage occurs in the spring than the other seasons. The lower part of the trunk is more heavily debarked than the upper. Debarking is progressively upward to the crown as the tree grows older. Home range, food habit and behavior of the red-bellied tree squirrel are under intensive study and some preliminary results have been obtained. Selection of tree species less susceptible to squirrel debarking has been a main step to control the damage. Intensive weeding and thinning may reduce much of the squirrel preferred habitat and therefore reduce damage. Leaving any natural hardwood forest within or adjacent to the coniferous plantations may provide squirrels with a more attractive cover and food supply. A rice-paraffin bait block of warfarin has been used to poison them with some success. But laboratory studies show klerat (brodifacoum) has a faster lethal efficacy than warfarin. Application of baits and other trapping methods to control squirrel populations need more study and evaluation.

Compensation for vertebrate pest damage

Compensation for wildlife damage to private property is recognized by the Alberta government as a short-term reimbursement to the property owner and a long-term investment in wildlife conservation. In 1978 the Alberta Problem Wildlife Committee recommended that problem wildlife management policies and programs should contain three basic factors: PREVENTION, COMPENSATION, and CONTROL or ANIMAL REMOVAL. These should be incorporated whenever possible in dealing with a particular species of problem wildlife or vertebrate pest. The Alberta government approved this philosophy as a reflection of traditional rights and fair treatment of landowners and as the basis for future programs. Compensation is paid for four types of confirmed wildlife damage: big game or game bird damage to cereals and forage; waterfowl damage to cereal crops; predator damage to livestock; and bear damage to bee equipment. The organization and operation of each of these programs are discussed in some detail.

Problem vertebrate management in Zimbabwe

Zimbabwe is the second largest agricultural producer in Africa and is responsible for the regional food security plan of the Southern Africa Coordination Conference member countries (SADCC). Problem vertebrate management and research is an important function of the Department of National Parks and Wildlife Management, which is also responsible for conservation of natural resources in national parks. The country still contains large populations of wildlife species that at times conflict with man and his agricultural interests. Problem vertebrates and methods of control are briefly outlined.

Changes in bait acceptance by rabbits in Australia and New Zealand

Control of rabbits, Oryctolagus cuniculus, by poisoned bait has been widely practiced in Australia and New Zealand for many years. Since the 1950s, Compound 1080 has been the active ingredient and yielded good results (ca 90% kills) when first used. Recent trails (1973-74) in New Zealand showed that the main reason for poor results obtained nowadays is the failure of many rabbits to eat bait. Recent trials in Western Australia showed that there has been a significant decline in effectiveness of rabbit control by baiting during the period 1958-1975. Shortcomings in operational technique and increased resistance to the poison 1080 were eliminated as being major possible causes of recent poor results. An increased incidence of neophobic behavior in rabbit populations as a result of artificial selection by poison baiting is suggested as the most likely explanation of our findings.

The red-eyed turtle dove (Streptopelia semitorquata) as an agricultural pest in Nigeria

Preliminary results compiled from visual observations and questionnaires indicated that a large variety of crops including soyabean, cowpea, groundnut, maize, rice, and sorghum were attacked at planting and seedling stages of growth by the red-eyed turtle dove (Streptopelia semitorguata). The social conditions under which this bird is protected, by social taboos and also as an attractive and common household pet in many parts of Nigeria, limit the control options that could be used to stop its deleterious activities. In the meantime, research efforts are being directed to the understanding of the population ecology and biology of the species as a prerequisite to determining appropriate control strategies.

Commensal rats: a threat to poultry production in Nigeria

Rats are now found in the majority of poultry houses in Nigeria. They usually inhabit roofs, interior of cupboards, electrical and gas appliances, holes in the soil and in walls and rubbish dumps. Extensive rat trapping yielded only two species, the cosmopolitan roof/ship rat (Rattus rattus} and the multimammate rat (Mastomys natalensis). The most outstanding types of damage, resulting in much economic loss, were the killing of chicks by decapitation and the infliction of deep wounds on adult birds. Breaking of eggs became a serious problem in a few cases. Damage to containers, bags, and feed consumption was usually of small proportions. Relief from damage in well-proofed and partially-proofed premises was obtained with the application of 5% alpha-chloralose in 95% milled maize or poultry feed or with Tomorin (a coumarin-derivative anticoagulant) applied at the ratio of 1 g. Tomorin in 19 g milled maize. Reinfestation within a few months was common in partially-proofed and unproofed premises, indicating a need for proper rat-proofing of poultry houses.

Rodent control in Barbados

The island of Barbados, in the eastern Caribbean, experienced an increase in the number of cases of leptospirosis between 1961 and 1971. With assistance from Pan American Health Organization/World Health Organization, multiple surveys were done to determine cause of the problem. The surveys concluded that (1) most cases of leptospirosis occurred just after heavy rainfall; (2) persons in the low socio-economic groups were more prone to acquire the disease; (3) rats (Norway rat, Rattus norvegicus, and black rat, R. rattus) were the major reservoir of leptospira organisms, with approximately one in three rats examined positive for leptospira organisms; and (4) persons performing specific types of work were the ones who are most frequently infected (e.g. farm, cane, and abattoir workers). The accomplishments of the newly-established Rodent Control Unit are described. After four years of operation, Barbadians are more aware of the rodent problem in the island today, as compared to the pre-Unit era, when rats and mice were commonly seen in public markets, bonds, warehouses, institutions, and dock areas. Today, in spite of the numerous eating places, stores, food and feed plants, etc., the rodent problem is relatively minor as compared with the past. The public is also more aware of the potential problems with rodents, and therefore quickly seeks help from the Rodent Control Unit. A systematic approach to rodent control has been achieved. Anticoagulant rodent baits (liquid and solid) are used extensively in the control work. Rodent Control work in Barbados is an ongoing process and is second-to-none in the Caribbean.

California registration procedures relative to vertebrate pesticides

The role of the California Department of Food and Agriculture (CDFA) is described in regard to its responsibilities in registering vertebrate pesticides and how this relates to Federal (EPA) registration. This includes its role in new product registrations, amended labels, 24(c) Special Local Need registrations, Experimental Use Permits, and Section 18 Emergency Exemptions. California registration requirements for vertebrate pesticides differ from the Environmental Protection Agency requirements in the following areas: Efficacy (performance data evaluation data are required); Biochemical Data (for rodenticides, data is required that describes the metabolic pathway and the mode of action in animal models suitable for extrapolation to human exposure); and Rodenticide Bait Safety (anticoagulant rodenticide baits intended for home use shall contain a dye, and baits containing strychnine shall be dyed with a green color additive).

Rodent problems relative to mechanical harvesting

As the number of crops that are mechanically harvested increases, the reports of rodent problems associated with those crops increase also. This report examines the rodent problems in mechanically harvested tomatoes and reports on work done in studying the effects of various border crops on rodent populations. It also looks at possible rodent management options available to growers of mechanically harvested crops.

Pulsed baiting--a new technique for high potency, slow acting rodenticides

The disadvantages of the acute, fast-acting, rodenticides are well understood by the specialist. However, despite poison-shyness and consequent short-lived, low efficacy rodent control, many users prefer "acutes" such as zinc phosphide to "first-generation" anticoagulants of the warfarin type. The techniques necessary for efficient use of the first-generation anticoagulants are often inappropriate, particularly in agriculture. High labour and bait inputs required are unacceptable and are, together with the need for area coordinated control programmes, significantly responsible for lack of widespread use of anticoagulants, even in those countries with a long history both of disastrous rodent damage to crops and rodent damage research and training centres. There are other problems, too, including widespread antithesis to prophylactic rodent control, perhaps in part due to the inherent low efficacy of acutes and the impractical nature (often leading to low efficacy) of first-generation anticoagulant baiting procedures. The advent of a highly potent but slow-acting rodenticide molecule, brodifacoum, has allowed the development of the pulsed baiting technique. This practical technique is highly effective and offers very significant savings both in bait and labour compared to first-generation anticoagulants, with excellent levels of control. Single applications are more effective than single applications of acute toxicants. Now used in agricultural and urban control programmes, the technique is proving to be very cost-effective and highly acceptable, both to educated campaign organisers and uneducated users. The theory, development and cost-effectiveness of the technique are considered together with the experience gained from its use over more than 4 million hectares of agricultural land. Use of the technique allows for the first time practical and efficient agricultural rodent control.

Green chopped bait for the control of the Oregon ground squirrel

This paper updates control operations in Modoc County, in northeastern California, for the Oregon or Belding ground squirrel, Spermophilus beldingi oregonus. With the increase of sprinkler irrigation and continual improvement in farming methods, we are giving the ground squirrel a better environment: the squirrels have more food and moisture, and their juvenile survival rate appears to have continued to increase. As in earlier years, we still have problems with bait-shyness or poor bait acceptance. It is now virtually impossible to obtain adequate acceptance of grain baits, forcing us to use “green” baits. Dandelion is the bait that is best accepted by the squirrel, but it is hard to obtain at the right time and in sufficient quantities. Cabbage is the next best green bait, and it is practical and economical to use. In 1972, we started treating fields using 1080-treated cabbage, and treatments resulted in 95% to 99% squirrel control. For efficiency, aircraft broadcasting has become the common method of application. This baiting program is quite effective, but it is not the cure-all. We still have several unresolved problems. We have fields in which squirrel control is so effective we can skip two or three years before retreating; however, other fields must be treated annually. In some cases, squirrels move in from nearby areas. Some problems with bait acceptance continue.

Current improvements in baiting pine and meadow voles

Excellent control of pine voles (Microtus pinetorum) and meadow voles (M. pennsylvanicus) was achieved with several commercially pelletized anticoagulant baits applied as single hand-placed or broadcast treatments. A new pelletized formulation of zinc phosphide (Zn3P2) was shown to kill approximately 30% more voles when compared to another surface-coated 2% Zn3P2 corn-and-oat formulation. Hand-placed cellophane or plastic-packaged rodenticides were effective when placed in vole runways under cinder blocks and split tires.

Aluminum phosphide (Phostoxin) as a burrow fumigant for ground squirrel control

The California ground squirrel (Spermophilus beecheyi) is widely distributed throughout California. It causes serious damage to agricultural crops. Tests were conducted to evaluate the fumigant aluminum phosphide (Phostoxin®) and to compare it to the commonly used gas cartridge. Treatments consisted of applying either a single-dose (two 3-gm tablets) or double-dose (four 3-gm tablets) of aluminum phosphide, or 1 U.S. Fish and Wildlife Service gas cartridge in each burrow in the study plots. The burrow opening was then plugged with 1 sheet of newspaper and sealed with soil. Burrows in the control plot were plugged with newspaper and sealed in the same manner. All plots were retreated 4 days after the initial treatment. Overall, the aluminum phosphide treatments were more effective than the gas cartridge treatments in terms of the reduction in the number of ground squirrels seen and in reopened burrows observed after treatment. The single-dose aluminum phosphide treatment was as effective as the double-dose treatment. The gas cartridge treatment required a greater amount of time for application and did not achieve very effective control. Many aspects of this fumigation technique remain unknown and continued research is necessary.

An IPM approach to rodent control on Midwestern farms

An Integrated Pest Management project in Nebraska is assisting farmers, particularly pork producers, in controlling dama9e caused by Norway rats, house mice, house sparrows, and starlings. A survey of pork producers to (1) determine the incidence of certain rodent and bird pests, (2) identify factors which contribute to pest damage and control, and (3) evaluate the project's impact, has been completed. Survey results are summarized. Continuing efforts to document economic damage caused by vertebrate pests are expected to enhance the program's impact.

A review of the secondary poisoning hazard potential to wildlife from the use of anticoagulant rodenticides

The utility and characteristics of the family of anticoagulant rodenticides are reviewed, including the new members difenacoum, bromadiolone, and brodifacoum. General considerations are given in investigating the likelihood of nontarget poisoning with rodenticides. The literature dealing with secondary poisoning studies and concerns with the use of anticoagulant rodenticides is reviewed. The utility of laboratory toxicity data versus field-generated exposure data is compared. Considerations of secondary poisoning by anticoagulants are reviewed as regards parameters such as specific predator-prey systems, biotopes, rodenticide use patterns, and risk-benefit assessments. Finally, examples of appropriate field studies proposed to assess specific secondary poisoning risk situations associated with particular anticoagulant usage patterns are exemplified by reference to studies conducted by ICI and outside researchers with brodifacoum rodenticide bait formulations.

Reducing starling depredations at livestock feeding operations through changes in management practices

Economic losses due to starling depredations at livestock feeding operations can be reduced by implementing management practices that limit access to or reduce consumption of grain products by starlings. Current farm management practices that reduce losses to birds are reviewed and alternate practices suggested. Management practices suggested include physical separation of feed from starlings, use of feed types that reduce the rate of consumption by starlings, and use of feeds that are either unpalatable or not physiologically usable by starlings. The reduction in starling numbers at feedlots resulting from these management practices may alleviate economic losses with a concomitant lesser dependence on shorter-term bird control measures involving scaring or lethal methods.

Urban blackbird roost survey - 1981

A brief description is given of 29 areas in the United States and Canada experiencing problems with blackbirds and/or starlings. The answers to an Urban Blackbird Roost Survey of these areas are tabulated and discussed. Suggestions for future urban roost management are presented.

Raptor-mimicking kites for reducing bird damage to wine grapes

Preliminary tests in California vineyards during 1979 and 1980 indicated that a raptor-mimicking kite suspended from a helium-filled balloon (kite-balloon or KB) could reduce bird damage to ripening wine grapes. Based on the results of both damage assessments and bird censuses, one KB per hectare, deployed for alternate 1-wk periods, reduced losses caused by birds by about 33% in 1979 and by an average of 48% in 1980 when compared with 1-wk control periods. Habituation by the birds to the KB appeared to reduce its effectiveness over time in 1979, but this problem was reduced in 1980 by regularly changing the KB components and deployment methods. Based on tests conducted in 1981, polyurethane tetroons (PTs) were the longest lasting of four balloons currently available for use in KBs, but in high winds they flew too close to the ground to keep kites aloft. Spherical balloons made of rubber had better flight characteristics but shorter longevity than the PTs. More testing is needed to evaluate the effectiveness of KBs for protecting entire vineyards during whole-season tests and to identify situations where their use may be cost-effective.

The cliff swallow--biology and control

Cliff swallows (Petrochelidon pyrrhonota) nesting in colonies on man-made structures can cause aesthetic problems and health hazards. Cliff swallows are migratory, wintering in South America and breeding throughout most of North America. Cliff swallows have a homing tendency to old colonies and are attracted to the gourd-shaped mud nests. Egg laying begins before nest construction is finished; clutch size averages 3 or 4 eggs. Renesting is common if a nest fails and some pairs may raise 2 broods in 1 nesting season. Cliff swallows may be present at a colony for up to 132 days. Cliff swallows are protected by the Migratory Bird Treaty Act of 1918, and a permit from the United States Fish and Wildlife Service is required for certain control activities. Successful control methods include nest removal by water hose or a pole, and exclusion using netting, poultry wire, or strip doors. Nest substrate modification is successful in some instances. Methods employed with little success or that remain unproven include metal spines, repellents, frightening devices, predator models, taped alarm calls, and a fresh coat of paint. Attention to architectural design may alleviate cliff swallow nesting problems.

Bird problems and their solution in Britain

The background and organization of research on bird pests in Britain are described and the main projects are outlined. Work is currently concentrated on bullfinches, starlings, rooks, and woodpigeons together with behavioural studies aimed at developing better bird scarers.

Pigeon control: An integrated approach

Reducing a pigeon population to a tolerable or minimal impact level is a subject about which one can find much antiquated and impractical information. Most technical literature reports on the biology of pigeons and associated disease factors. The intention of this paper is to describe the practical application of large-scale pigeon population reduction programs that have been at least 90% effective in 45 out of 46 cases over the past four years. Human relations, exclusion, trapping, toxic perches and Avitrol are discussed.

Assessment, understanding and management of blackbird-agriculture interactions in eastern Canada

The major results of recent research on the problem of red-winged blackbird (Agelaius phoeniceus) damage to field corn (Zea mays) in eastern Canada are reviewed. In the area of damage assessment, an indirect approach relying on energetic considerations appears to provide a rapid and inexpensive means for generating reliable damage estimates. The identification of pronounced compositional changes in roost populations has provided a more accurate means for predicting the impact of any management technique relying on population reduction at roosts. Investigation of the interaction of blackbirds and insects revealed that prey species conform to general patterns of coloration, mobility and the type of substrate from which they are taken. Also, a detailed examination of European corn borer (Ostrinia nubilalis) populations near a blackbird roost indicated that there was a tangible benefit to agriculture derived from blackbird predation of corn borers. An evaluation of blackbird population reduction through both surfactant spraying of spring roosts and through the use of decoy traps indicated that neither represented a viable solution to the crop damage problem.

Bird damage to sunflowers in the Sacramento Valley, California

Damage caused by birds to ripening sunflower was evaluated in 60 fields (about 70% of all planted fields) in the Sacramento Valley, California, during 1980 and 1981. Overall monetary losses were roughly $6,800 (24 fields) and $7,400 (36 fields) in 1980 and 1981, respectively. The percentage losses estimated for the individual fields were low, ranging from O to 5.4% of the crop; in about two-thirds of the fields, losses were <0.5%. For the 12 fields with the highest (≥1 .0%) damage, the average per acre monetary loss was roughly $18. Damage levels within local areas were relatively constant between the two years. Although several species of birds caused damage, house finches (Carpodacus mexicanus) were apparently most important. Their foraging behavior differed from that of blackbirds, which fed extensively on insects in addition to sunflower. The presence of large numbers of blackbirds or finches in fields was not always an indication of bird damage. Additional research may lead to recommendations for alleviating the moderate losses which a few growers now incur.

A comparison of selected rodenticides for the control of the common Valley pocket gopher (Thomonys bottae)

The common valley pocket gopher (Thomomys bottae) has become a serious agricultural pest in certain regions of the Lower Colorado River Basin. The mechanical burrow-builder is the most economical and effective method of controlling this pest, although many growers and some researchers have reported less-than-satisfactory results when using this technique with currently available rodenticides. Six formulations of three toxicants including strychnine, zinc phosphide, and diphacinone were applied with the burrow-builder to assess their efficacy. Results indicated that negligible control is achieved with 0.35 and 0.5% strychnine, although these are the most commonly used formulations in Arizona. Diphacinone also produced negligible control. Zinc phosphide was clearly the most effective of the compounds tested with 45% control achieved. More work with this compound is warranted.

Rodent repellents for planted grain

Thirteen-lined ground squirrels (Spermophilus tridecemlineatus) and other small rodents damage corn (Zea mays) stands by digging and consuming planted seeds and young seedlings, particularly in reduced-tillage fields. The use of reduced-tillage systems such as ecofarming provides greater dryland crop yields, conserves moisture, reduces soil erosion, and provides suitable habitat for ground-nesting birds. The habitat available in these fields also allows various species of rodents to thrive. Reduced-tillage farming is expected to increase markedly in the years ahead; thus, rodent problems will increase as well. Seed repellents offer a promising and cost-effective method of controlling rodent damage to planted corn in some areas. This paper reviews repellents for this use and describes repellency studies currently in progress with the compounds methiocarb [3,5-dimethyl-4-(methylthio) phenol methylcarbamate] and thiram (tetramethylthiuram disulfide).

Dispersal and some implications for control of the California ground squirrel

Data from current research and from the literature indicate that a knowledge of dispersal of the California ground squirrel can help to develop control strategy. An understanding of the rate and extent of dispersal may help reduce poor results due to patchy control. A knowledge of dispersal distance can help to determine the size of a buffer zone of control which may reduce the rate of reinvasion. The seasonal timing of dispersal is predictable in the California ground squirrel, and this can help to establish follow-up control.

Strychnine residue studies and their implications in rodent control

Applications of 0.29, 1.0, 2.63, and 5.26% strychnine-impregnated grain baits were applied below ground to 10' x 10' plots of alfalfa to determine translocation of strychnine from the soil to plants. Four replicates of each concentration were made and the alfalfa analyzed for strychnine residues. Four 10' x 10' plots were utilized as controls. Plant samples were taken on Day 1, Day 9, and Day 14. Strychnine was not detected in any of the samples above the limit of detectability (0.02 ppm). Apples from trees subjected to a normal, 1 x normal, and a 3 x normal gopher control strychnine bait application were sampled and analyzed for residues. Four replicates were used and samples were taken on Day 4, Day 14, and Day 28. Analytical methods were identical to those utilized for alfalfa with normal to 3 x normal application rates of strychnine baits. There was no detectable strychnine translocated from the soil to the fruit of the apple trees. When using an authorized application rate of strychnine-impregnated bait utilized in a gopher control program, there is apparently no translocation of strychnine from the soil to the harvestable crops involved in this study. Because of the strong sorption characteristics of strychnine, even on soils of low cation exchange capacity (6.8 meq/100 g), mobility in soils was found to be minimal.

Evaluation of zinc phosphide bait for pocket gophers control on forest land

Laboratory bioassays and field tests were conducted to determine if zinc phosphide baits would control pocket gophers in forest plantations. Zinc phosphide baits generally were less effective than the strychnine alkaloid-oat bait commonly used by forest managers to control gophers. However, a carrot bait with 0.75% zinc phosphide showed potential as a substitute for strychnine. Size of carrot bait and grooming activity of gophers were identified as important factors affecting efficacy of baits.

Responses of caged red-winged blackbirds to methiocarb on wild rice

Red-winged blackbirds (Agelaius phoeniceus) were offered a choice between cultivated wild rice (Zizania aguatica) treated with methiocarb and untreated wild rice. Unhulled wild rice soaked in methiocarb solution was highly effective in repelling blackbirds at residue levels <132 ppm. The responses of blackbirds to methiocarb residues <132 ppm on soaked rice were variable. Most of the blackbirds conditioned to avoid treated rice at 132 ppm of methiocarb were subsequently repelled by treated rice with residues as low as 30 ppm.

A new system for delivery of predacides or other active ingredients for coyote management

Preliminary trials suggest that the delivery system or unit described may prove to be a highly selective and effective system for delivering drugs or chemicals to coyotes. The goose egg-size unit's selectivity and effectiveness relies heavily on a newly developed synthetic olfactory coyote lure based on trimethylammonium decanoate (TMAD). The coyote is attracted to the unit, which is placed at ground level, by this highly selective scent lure which elicits a biting and chewing behavior. When a coyote bites or chews the exposed part of the unit, it punctures a plastic reservoir packet containing 10 to 15 ml of viscous sucrose liquid, which serves as a taste attractant, a carrier (diluent) of the active ingredient (i.e., toxicant, chemosterilant, etc.), and as a way of diluting the toxicant, since the amount of active ingredient consumed depends upon the amount of liquid consumed. The sucrose is avidly consumed by coyotes, insuring that coyotes will ingest most of the active ingredient.

Twentieth anniversary of Vertebrate Pest Conferences in California

The author summarizes the history of the first twenty years of the Vertebrate Pest Conference, which was first held in Sacramento, CA in 1962. He discusses the reasons the Conference and its resulting published Proceedings became established, with details on individuals and agencies that were involved in its inception. The Conference’s evolution and growth are summarized.